1. Field of the Invention
The present invention relates to an information processing apparatus and a method for processing information, and more specifically, to processing executed for printing an image including a tint block image, which restrains people from using duplicates and the like, in a system configured by having the information processing apparatus, such as a personal computer, and the printing apparatus, such as a printer.
2. Description of the Related Art
Conventionally, in order to prohibit copying a ledger sheet, a resident card, and the like, or restrain people from doing so, papers on which special printing is given, papers called anti-counterfeit paper have been used. The anti-counterfeit paper is a paper in which characters or the like such as “COPY” is embedded to be hard to recognized by a human eye when the paper is in a state of an original and to show up on the copied paper when the original is copied using a copying machine or the like. Thereby, people can visually distinguish a print sheet as the original from the duplicate made by copying the original, easily. The use of this anti-counterfeit paper as an original causes those who copy the original to hesitate to use duplicated papers. Moreover, the anti-counterfeit paper gives a mental restraint effect of inhibiting an act of copying itself. The reason why characters in the original of the anti-counterfeit paper needs to be hard for people to recognize is to enable people to distinguish between the original and the duplicate definitely. If characters such as “COPY” is recognizable to such an extent that people can clearly recognize it even in the original, there may occur the possibility that people recognize it as the duplicate and such paper does not make a sense as the anti-counterfeit paper. Wicker (U.S. Pat. No. 5,788,285) and Mowry et al. (U.S. Pat. No. 6,000,728) disclose arts for manufacturing such an anti-counterfeiting paper.
However, since the anti-counterfeit paper like this is made by fully employing a special printing technology, it comes with a problem of high cost compared to normal papers. Moreover, the anti-counterfeit paper can make only characters that are set at the time of manufacturing show up. Therefore, an application of the anti-counterfeit paper and characters being set are limited. That is, the conventional anti-counterfeit paper lacks flexibility regarding applications because of a matter on its manufacture.
On the other hand, as various contents are being digitized, the contents of ledger sheets, a resident card, or the like are being transformed into digital data similarly. However, digitization for handling of these ledger sheets and resident cards, such as use of these documents, is still in a transition phase. Consequently, the contents of digital data formed using a computer is likely to be outputted on papers with a printer or the like for subsequent use.
Under such circumstances, significant improvement in printer performance has been achieved in recent years, and this is one of cause for a technology, which makes it possible to print out a paper on demand that has the same effect as the conventional anti-counterfeit paper using a computer and a printer, to attract an attention. Japanese Patent Application Laid-open No. 2001-197297 and Japanese Patent Application Laid-open No. 2001-238075 disclose technologies whereby, when contests data formed using a computer is printed out with a printer, an image called tint block (a copy-forgery-inhibited pattern) is also outputted with superposed on the background of the contents data. The tint block image is an image that is recognized only as a simple pattern or a mere background color in the original (a printed matter outputted by a printer) to the human eye, but, when it is copied, will show up as predetermined characters or the like in the duplicate. Thereby, the same restraint effect as the anti-counterfeit paper can be given to those who copied.
In the case that the contents are printed out together with a tint block image generated by a computer, being superposed thereon, naturally a normal printing paper or the like can be used. Therefore, this technology has an advantage in terms of cost in comparison with the technology using the anti-counterfeit paper. Moreover, the tint block image can be generated when the contents are outputted by printing. Thereby, characters or the like that will be made visible at the time of copying can be set freely. Further more, there is also an advantage that dynamic information, such as a user name who executed printing and printout time and date, can be made to show up as the characters.
The tint block image, as discussed above, is one that, when being duplicated, visualizes a predetermined character or the like that could not be recognized before duplication, therefore restrains people from using the duplicate, and realizes an effect of enabling people to visually identify what the people sees to be the duplicate, in other words, not to be the original easily. In order to realize this effect, the tint block image is basically composed of two areas: an area which remains (shows up) in the duplicate when being copied, and an area which disappears in the duplicate or becomes too light-colored to recognize compared to the image remaining area. These two areas, as being printed, are of almost the same density, and therefore no one can recognize that characters etc., such as “COPY” that will become visible by duplication are hidden (embedded) therein at first sight, in a macroscopic sense. However, in a microscopic sense, for example, in a level of printed dots, these two areas have different characteristics, respectively, as will be shown below.
Hereafter, an image that will show up by duplication is called a “latent image” and an image that will disappear or become light-colored is called a “background” for convenience. The tint block image is basically composed of the latent image and the background image. Moreover, there is a case where the tint block image also includes a below-mentioned camouflage image. Incidentally, there may be a case where the latent image is called a foreground as a term related to a user interface.
Note that tint block printing is not limited to the above-mentioned composition, and the tint block image may be composed in such away that characters, such as a “COPY”, a logo, or a pattern will be rendered (will become visible) as an recognizable image to the human eye in the duplicate. That is, even if the characters “COPY” are rendered as outlined characters in the duplicate, it will achieve its object as tint block printing. In this case, needless to say, the characters of “COPY” are generated as a background image.
Now, in the case of dot printers, such as of electro-photographic and ink jet systems, an area which will remain in the duplicate (latent image section or foreground section) consists of sets of concentrated dot masses. The area which will disappear or be reproduced with thinner density (background section) than the image density in the area which will remain consists of sets of dispersed dots. Moreover, in a state where the tint block image is printed, the density of the whole tint block image can be made almost uniform by setting the images in such a way as to have almost equal density in respective areas.
FIG. 24 is a view showing these two areas. As shown in this figure, the tint block image is composed of both the background section in which dots are arranged dispersedly and the latent image section in which concentrated dot masses are arranged. These two areas can be generated by mutually different half tone dot processing and dither processing. In the case where the tint block image is generated using the half tone dot processing, half tone dot processing with a small number of lines is suited for the latent image and that with a large number of lines is suited for the background section. In the case where the tint block image is generated using dither processing, dither processing using a dot concentration type dither matrix is suitable for the latent image section, and dither processing using a dot dispersion type dither matrix is suitable for the background section.
Generally, the copying machine has critical points in reproducing capability that depends on input resolution of reading fine dots of a manuscript and output resolution of reproducing fine dots. In the case where the dot in the background section of the tint block image is formed smaller than the critical point of dots that the copying machine can reproduce and the dot masses in the latent image section thereof are formed larger than the critical point, an image composed of larger dot masses of the tint block image is reproduced and an image composed of smaller dots is not reproduced, in the duplicate by copying. As a result, the latent image will be made visible. Moreover, even in the case where dispersed small dots are not completely disappeared by copying, i.e., in the case where the density of the background section is low compared to that of concentrated dot masses, relatively the latent image can be recognized more markedly.
FIGS. 25A and 25B are views showing visualization of a latent image. FIG. 25A is a view corresponding to a state where the tint block image is printed. FIG. 25B is view corresponding to a duplicate obtained when FIG. 25A was copied by a copying machine. From FIG. 25A and FIG. 25B, it may be understood that the latent image by the concentrated dot masses will show up and the background by the dispersed dots will disappear.
Further, it is also known well that a technique called the “camouflage” for making it difficult to recognize a latent image embedded in the original is applied to the tint block image. The camouflage is a technique of arranging a pattern whose density is differentiated from those of the latent image section and the background section to be superposed on the tint block image. The tint block image to which the camouflage is applied has an effect that the camouflage image whose density is different from those of the latent image section and the background section becomes noticeable and the latent image section becomes further less noticeable. Moreover, the camouflage image has an effect of giving a decorative impression to a printed matter.
FIG. 26A shows a tint block image to which no camouflage image is given. FIG. 26B shows a tint block image to which a camouflage image is given. In order to make it easy to recognize a visualized latent image in the duplicate after duplication, it is desirable that dots constituting the camouflage image are made not to be reproduced in the duplicate. This can be realized by, for example, drawing the camouflage image as an outlined image, as shown in FIG. 26B.
However, in the case of performing printing to which the tint block printing described above is applied, if the density of the tint block image is equal to or close to the density of the contents to be printed, i.e., the image to be printed out (hereinafter, also referred to as a print object), there is the possibility that printing of the tint block image makes the print object hard to recognize.
As described above, a fundamental formation of the tint block image printing is such that the tint block image is printed all over the printable area (hereinafter, also referred to as a physical page) in a printing paper in the form of watermark printing or superposition printing, as will be described later with reference to FIG. 17, FIG. 18, and FIG. 19. This is done by adopting the idea of the anti-counterfeit paper in which the above-mentioned characters, such as COPY PROHIBITED, is printed in advance. One reason of adoption is that, even if the image to be printed out is printed in any positional relationship to the printing paper, an image visualized from a latent image is made to show up in a position free from interference with a copied print object. As a result, the whole of the printout image is printed being superposed on the tint block image. In this case, if the printout image has the density equal to or close to that of the tint block image over the whole area or partly, the printout image is often hard to identify. More specifically, the following cases are conceivable: the outline of the printout image becomes hard to recognize in the case where the printout image and part of the tint block image adjacent to that image have close density values; and the contents of the printout image itself become hard to identify in the case where the printout image and part of the tint block image superposed on that image have close density values.
FIGS. 27A and 27B are views explaining one example of the above-mentioned interference of density between the printout image and the tint block image. FIG. 27A shows an example of a printout that is printed without performing the tint block processing. Since the tint block processing is not performed, a background 512 is of a color of the ground of printing paper, whose density is different from the density of an ellipse 511, the print object in the center of the printing paper. Then the print object can be easily recognized because of this difference in density. In contrast to this, FIG. 27B shows an example of a printout when the tint block processing is performed. The density of the central ellipse 511 is close to that of the tint block image 513, which makes it difficult to identify the ellipse 511.